This invention relates to cartridge cases, and more particularly to composite cartridge cases made up of two components, including a tubular casing component having a mouth portion for receiving a projectile, and a separate base component for mounting a primer and providing a rim for extraction. The principle purpose of the two component parts is to permit the use of dissimilar materials for the components, usually comprising a softer and more ductile material such as brass for the tubular casing component and a harder high strength material such as steel for the base component.
Examples of such composite cases are described and claimed, for example, by U.S. Pat. No. 3,099,958 issued Aug. 6, 1963 to B. K. Daubenspeck, and U.S. Pat. No. 3,977,326 issued Aug. 31, 1976 to Ramond Anderson, and John J. Scanlon.
The general objectives of the present invention are to provide a re-usable two component case of great strength which can be easily disassembled by using a threaded joint to join the two components, and easily sized (reduced in size or formed to nominal cartridge dimensions) using conventional steel sizing dies. By using a softer material than the base for the tubular casing component and properly proportioning the two components so an excessive amount of the harder base does not enter the sizing die during sizing operations, conventional steel sizing dies can be utilized for sizing operations. By having a base component which is solid around the primer pocket, removing only that material needed to create an extraction groove, and using a high strength material such as steel, a cartridge case is created which is unusually resistant to deformation or failure from very high gas pressure in the critical base region.
Additionally, with the proper shape and proportions given in this invention, the forward section (tubular casing component) can be made from existing conventional cartridge cases. This tubular casing can also be made from cases which have been manufactured utilizing a slightly modified heading operation eliminating the need for reducing the diameter of the rear of the tubular casing prior to threading (male threads). Using existing conventional cartridge cases or cartridge cases modified only in the heading operation allows the use of existing cartridge case manufacturing facilities for production of the cartridge cases from which the tubular casings are manufactured.